(1) Field of the Invention:
This invention relates to a novel antifouling coating which is coated on underwater substrates, for example, underwater structures such as ships, marine tanks, buoys and the water conduit raceway tubes in the thermoelectric power plant, coastal industrial seawater plants, and fishing nets such as cultivating nets and stationary nets, and which is non-toxic and has long-term antifouling properties.
(2) Description of the Prior Art:
It is a well known fact that various kinds of animals and plants such as barnacle, oyster, ascidian, polyzoan, serupulas, sea lettuce and green laver live in the waters including the seawater, and adhere and grow on the surface of the aforementioned underwater substrates, resulting in doing various damages. Such various damages are done that, adhesion thereof onto the bottom of a ship increases resistance to water to increase shipping service fuel charge, that in the case of the fishing nets, culture productivity is reduced, and so forth.
In order to prevent the aforementioned damages, the antifouling coating prepared by incorporating a toxic antifouling agent such as an organotin compound, copper suboxide or the like, has conventionally been coated thereon. The antifouling mechanism by use of the aforementioned antifouling coating is such that the aforementioned antifouling agent is always leached from the coating film into the water to kill larvae, etc. of the aforementioned underwater animals and plants. However, toxicity of the antifouling agent in the aforementioned antifouling coating is undesirable from the standpoints of the safety and hygiene during the preparation and coating of the aforementioned antifouling coating, and moreover the leaching of the antifouling agent into the water has the possibility of polluting the sea and marine resources.
Recently, researches and developments of the so-called non-toxic antifouling coating free of the toxic antifouling agent have been made. However, the non-toxic antifouling coatings, which have been proposed so far, contain as the major components or are prepared by incorporating silicone rubber, silicone oil, Teflon resin, paraffin wax, and the like, and are all such a type that the surface energy of the coating film is reduced to be water repellent so that adhesion properties thereof to adhesive protains, which are secreted from the interior of the body of the underwater living things when they adhere thereonto, may be reduced to a minimum. However, the results of studies on the aforementioned non-toxic antifouling coatings showed that they have such unsatisfactory antifouling properties as to be significantly poorer compared with the antifouling coatings containing the aforementioned toxic antifouling agents to such an extent that much adhesion of the underwater living things onto the surface thereof was observed several months after submersion under water varying depending on the water area to be unsatisfactory from the practical point of view.